US6620707B1 - Heat conductor, especially for a sensor, and method for producing such a heat conductor - Google Patents

Heat conductor, especially for a sensor, and method for producing such a heat conductor Download PDF

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Publication number
US6620707B1
US6620707B1 US09/787,081 US78708101A US6620707B1 US 6620707 B1 US6620707 B1 US 6620707B1 US 78708101 A US78708101 A US 78708101A US 6620707 B1 US6620707 B1 US 6620707B1
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United States
Prior art keywords
platinum
heating conductor
precious metals
sintering
paste
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Expired - Fee Related
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US09/787,081
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English (en)
Inventor
Detlef Heimann
Bernd Reinsch
Alexander Bischoff
Juergen Werner
Lothar Diehl
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Robert Bosch GmbH
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Robert Bosch GmbH
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Assigned to ROBERT BOSCH GMBH reassignment ROBERT BOSCH GMBH ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: REINSCH, BERND, WERNER, JUERGEN, BISCHOFF, ALEXANDER, DIEHL, LOTHAR, HEIMANN, DETLEF
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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/10—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor
    • H05B3/12—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material
    • H05B3/14—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material the material being non-metallic
    • H05B3/141—Conductive ceramics, e.g. metal oxides, metal carbides, barium titanate, ferrites, zirconia, vitrous compounds
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403—Cells and electrode assemblies
    • G01N27/406—Cells and probes with solid electrolytes
    • G01N27/4067—Means for heating or controlling the temperature of the solid electrolyte
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/10—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor
    • H05B3/12—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material

Definitions

  • the present invention relates to a heating conductor, in particular for a sensor, and a method for manufacturing the heating conductor.
  • Heating conductors of the type mentioned are known and are used for setting an adjustable operating temperature of the sensor. Sensors of this type are marked by an advantageously layered design, individual layers being obtained using silk-screen printing, laminating, stamping, sintering, or the like. If the sensor acts to determine an oxygen concentration from the exhaust gases of an internal combustion engine, it contains essentially the following features:
  • a measuring electrode is arranged on a surface of the sensor and, if appropriate, is covered by a porous protective layer. Underneath the measuring electrode is located a layer composed of a solid electrolyte, that layer being followed by a reference electrode. The reference electrode in turn is situated on a reference gas channel, which is filled with a reference gas. To bring the sensor element to a specifiable temperature, there is arranged underneath the reference gas channel the heating conductor, which is optionally covered by an electrical insulator.
  • the electrodes and the heating conductor are usually manufactured by sintering a mixture made of a metal oxide powder and a metal powder (cermet).
  • the heating conductor must have a sufficient current carrying capacity, which is all the more beneficial, the lower the porosity of the heating conductor. Therefore, for manufacturing the heating conductor, the highest possible sintering temperature is preferred.
  • Known heating conductors are usually made of a cermet composed of platinum and a metallic oxide, such as aluminum oxide. From U.S. Pat. No. 5,787,866, it is known to manufacture the heating conductor out of platinum Pt and a further precious metal from the group Rh, Pd, Ir, Ru, and Os, in order to increase its resistance to corrosive processes. Since the measuring and reference electrodes preferably also contain platinum as a metallic component, the sintering temperature can only be selected as a compromise between the two objectives with respect to porosity.
  • the known heating conductors have only insufficient operating stability on account of the oxidation of the platinum and the coagulation of the Pt. Because of aging processes of this type, the sensor can be subject to a total failure.
  • a heating conductor manufactured with a cermet that has added to it at least two further precious metals thereby allowing a lower sintering temperature.
  • a lower sintering temperature creates a heating conductor with a low porosity, and, reduces the influence of temperature fluctuations in the sintering furnace.
  • a heating conductor of this type demonstrates a significantly lower susceptibility to oxidation, so that the heating conductor has an increased service life.
  • the cermet should have the composition
  • a composition of the cermet of 6.6% wt Rh and 3.3% wt Au, as well as either 88.1 % wt Pt and 2% wt Al 2 0 3 or 80.7% wt Pt and 9.4% wt Al 2 0 3 have proven to be especially advantageous with respect to the resistance and the manufacture of the heating conductor.
  • the sintering method As a function of the embodiment of the sintering method and/or of a property of the metals used for manufacturing the cermet, it is possible to influence the distribution of the metal components in the cermet. Thus it is conceivable that cermets in which heterogeneous alloys of platinum and the further precious metals are present are manufactured in a controlled manner. In this manner, the resistance of the heating conductor can additionally be influenced.
  • the method steps necessary in manufacturing the heating conductor with respect to the use of platinum-precious metal alloys can be developed in an advantageous manner.
  • precious metals can precipitate out in the area of the measuring and reference electrodes due to their high vapor pressure.
  • this can lead to a falsification of the measuring value of the sensor.
  • This can be prevented during the sintering in the sintering furnace if a sufficiently large air exchange is assured, for example using a blower.
  • the sintering furnace be designed such that a temperature gradient is present within the sensor element in the furnace.
  • the sensor is arranged in the sintering furnace such that the heating conductor is located in an area having the lowest temperature, so that the precious metal only condenses in this area.
  • FIGURE shows a cross-sectional view of a sensor including a heating conductor.
  • Sensor 12 has a heating conductor 10 , which is surrounded by an electrical insulator 24 .
  • sensor 12 has a measuring electrode 14 , which is optionally covered by a porous protective layer 22 .
  • Beneath measuring electrode 14 is a layer 20 made of a solid electrolyte and then a reference electrode 16 .
  • Reference electrode 16 in turn is situated on a reference gas channel 18 which is filled by a reference gas.
  • a sensor 12 of this type is usually used for determining an oxygen concentration, in particular in exhaust gases of internal combustion engines.
  • a potential which fluctuates in accordance with the oxygen content in the exhaust gas at measuring electrode 14 , is compared with a potential on reference electrode 16 .
  • the potential on reference electrode 16 is, inter alia, a function of the oxygen concentration in the reference gas and of the temperature. An adjustment of the temperature can be achieved using heating conductor 10 .
  • measuring and reference electrodes 14 , 16 must have sufficient porosity in order to have a sufficiently large 3-phase boundary surface. Stated in simplified form, the adjustment of the potential of measuring and reference electrodes 14 , 16 takes place in the area of 3-phase boundary surface.
  • the porosity can be substantially influenced by the level of the sintering temperature. High sintering temperatures, in this context, lead to a dense sintering of heating conductor 10 , but also of electrodes 14 , 16 .
  • Sensor 12 is marked by its advantageously layered construction, the individual layers being obtained by silk-screen printing, laminating, stamping, sintering, or the like.
  • silk-screen printing in this context, pastes are applied to a ceramic foil, which, after the sintering, form the individual layers.
  • Electrodes 14 , 16 and heating conductor 10 in this context, are formed from layers that are composed of a cermet, a metal oxide being used as the support structure and a metal being used as the conductor.
  • a paste made of a metallic powder and a metallic oxide powder, producing the layer is applied to a substrate and is then sintered.
  • platinum is used as a metal for heating conductor 10 and electrodes 14 , 16 , and aluminum oxide is preferred as a ceramic material in heating conductor 10 .
  • aluminum oxide is preferred as a ceramic material in heating conductor 10 .
  • ZrO 2 is used as the ceramic material.
  • the dense sintering of heating conductor 10 can be realized at a substantially lower sintering temperature than is the case when pure platinum is used. After the sintering, an at least ternary platinum-precious metal alloy exists.
  • the further precious metals are selected from the group Pd, Rh, Au, Ag and Ir. Overall, the cermet should have a composition of
  • cermet having the composition Pt 88.1% wt, Al 2 0 3 2% wt, Rh 6.6% wt and Au 3.3% wt demonstrated a resistance of 3.6 ⁇ . If the concentration of Al 2 0 3 rose to 9.4 % wt and the concentration of Pt dropped to 80.7% wt, then the resistance rose to 9 ⁇ .
  • the proportion of metal oxide, specifically aluminum oxide, in the cermet amounts to 0.5 to 50% wt.
  • the precious metals can be introduced into the method in various ways. Thus, it is possible to add them to the paste directly as a powder. In addition, it is possible to use platinum powder to which precious metals have already been added or to apply the precious metals as a layer on the grains of the platinum powder, for example using chemical processes or pulverization. The latter method can result in the fact that the alloy, which preferably melts at a lower temperature, forms during the sintering process only in one contact area of the grains, so that after the sintering there exists overall a heterogeneous, at least ternary platinum-precious metal alloy.
  • the sintering temperature is selected as a function of at least one of the melting temperatures of the precious metals or of the platinum-precious metal alloy. Since these temperatures are lower than the melting temperature of platinum, a dense sintering of heating conductor 10 occurs at already essentially lower temperatures. Due to the lower temperatures, existing measuring and reference electrodes 14 , 16 are also prevented from losing their porosity.
  • precious metals can pass over into the gas phase due to their partially high vapor pressure.
  • the resulting precious metal vapors can in turn condense in various areas of sensor 12 . Inter alia, this can occur in the area of measuring and reference electrodes 14 , 16 . Since precious metals, for example gold, have a very high affinity for gases such as carbon monoxide, it can result in a covering of a surface of electrodes 14 , 16 , and this can lead to falsified measuring results of sensor 12 .
  • a poisoning of the electrodes in this manner can be avoided in two ways.
  • a sufficiently large air exchange must take place in the area of the substrate.
  • this can be brought about by using a suitable blower in the sintering furnace.
  • the sintering furnace in such a case is advantageously equipped with a condensation area, at which the gaseous precious metals can be precipitated out.
  • the sintering furnace can be designed such that, during the sintering process, it has a temperature gradient in the area of the ceramic foil and the temperature in the area of the paste forming heating conductor 10 is the lowest possible. Overall, using the two methods, a condensation of gaseous precious metals can be avoided in the area of measuring and reference electrodes 14 , 16 .

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  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Biochemistry (AREA)
  • Molecular Biology (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Analytical Chemistry (AREA)
  • Ceramic Engineering (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Measuring Oxygen Concentration In Cells (AREA)
  • Investigating Or Analyzing Materials By The Use Of Fluid Adsorption Or Reactions (AREA)
  • Surface Heating Bodies (AREA)
  • Resistance Heating (AREA)
US09/787,081 1999-07-13 2000-06-15 Heat conductor, especially for a sensor, and method for producing such a heat conductor Expired - Fee Related US6620707B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE19932545A DE19932545A1 (de) 1999-07-13 1999-07-13 Heizleiter, insbesondere für einen Meßfühler, und ein Verfahren zur Herstellung des Heizleiters
DE19932545 1999-07-13
PCT/DE2000/001990 WO2001004915A2 (de) 1999-07-13 2000-06-15 Heizleiter, insbesondere für einen messfühler, und ein verfahren zur herstellung des heizleiters

Publications (1)

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US6620707B1 true US6620707B1 (en) 2003-09-16

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US09/787,081 Expired - Fee Related US6620707B1 (en) 1999-07-13 2000-06-15 Heat conductor, especially for a sensor, and method for producing such a heat conductor

Country Status (6)

Country Link
US (1) US6620707B1 (ja)
EP (1) EP1145255B1 (ja)
JP (1) JP4532047B2 (ja)
CN (1) CN1201344C (ja)
DE (2) DE19932545A1 (ja)
WO (1) WO2001004915A2 (ja)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040188321A1 (en) * 2003-03-24 2004-09-30 Sumitomo Electric Industries, Ltd. Wafer holder for semiconductor manufacturing device and semiconductor manufacturing device in which it is installed
US20040247844A1 (en) * 2003-03-28 2004-12-09 Seiko Epson Corporation Ceramic material coating method and ceramic film
US20070176077A1 (en) * 2006-01-30 2007-08-02 Science Applications International Corporation System and method for correction of turbulence effects on laser or other transmission
CN102809634A (zh) * 2012-08-28 2012-12-05 济南大学 一种基于钯杂化四氧化三铁纳米材料构建的气敏传感器
EP2763143A4 (en) * 2011-09-27 2016-01-27 Tanaka Precious Metal Ind CONDUCTIVE PARTICLES, METALLIC PASTE, AND ELECTRODE
CN106018496A (zh) * 2016-05-20 2016-10-12 太原理工大学 一种高灵敏度低工作温度乙醇气体传感器元件的制备方法

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10225149A1 (de) 2002-06-06 2004-01-15 Robert Bosch Gmbh Sensorelement
DE102004016008A1 (de) * 2004-04-01 2005-10-20 Bosch Gmbh Robert Keramisches Heizelement für Gassensoren
DE102013217198A1 (de) * 2013-08-28 2015-03-05 Robert Bosch Gmbh Sensorelement zur Erfassung mindestes einer Eigenschaft eines Messgases in einem Messgasraum
DE102014209029A1 (de) * 2014-05-13 2015-11-19 Robert Bosch Gmbh Platincermet und Verfahren zu seiner Herstellung

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4500412A (en) * 1981-08-07 1985-02-19 Kabushiki Kaisha Toyota Chuo Kenkyusho Oxygen sensor with heater
JPS62250151A (ja) 1986-04-24 1987-10-31 Alps Electric Co Ltd サ−メツト
US4863583A (en) * 1987-04-24 1989-09-05 Ngk Insulators, Ltd. Electrode structure of an oxygen sensing element
US5142266A (en) 1987-10-01 1992-08-25 Robert Bosch Gmbh Ntc temperature sensor and process for producing ntc temperature sensing elements
JPH07290198A (ja) 1994-04-28 1995-11-07 Nittetsu Hard Kk 耐熱性表面層を形成した連続鋳造モールド
US5787866A (en) 1996-04-12 1998-08-04 Denso Corporation Air-fuel ratio sensor
EP0859233A2 (en) 1997-02-12 1998-08-19 Ngk Insulators, Ltd. Gas sensor
US6274016B1 (en) * 1998-06-29 2001-08-14 Kabushiki Kaisha Riken Nitrogen oxide gas sensor

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62238455A (ja) * 1986-04-09 1987-10-19 Ngk Insulators Ltd 酸素分析方法及び装置
EP0720018A1 (en) * 1994-12-27 1996-07-03 General Motors Corporation Thick film heater with multiple inks for the serpentine and the lead
DE19713904A1 (de) * 1997-04-04 1998-10-08 Bosch Gmbh Robert Verfahren zur Herstellung eines Sensorelementes
JP3783375B2 (ja) * 1997-11-10 2006-06-07 株式会社デンソー 空燃比センサ素子

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4500412A (en) * 1981-08-07 1985-02-19 Kabushiki Kaisha Toyota Chuo Kenkyusho Oxygen sensor with heater
JPS62250151A (ja) 1986-04-24 1987-10-31 Alps Electric Co Ltd サ−メツト
US4863583A (en) * 1987-04-24 1989-09-05 Ngk Insulators, Ltd. Electrode structure of an oxygen sensing element
US5142266A (en) 1987-10-01 1992-08-25 Robert Bosch Gmbh Ntc temperature sensor and process for producing ntc temperature sensing elements
JPH07290198A (ja) 1994-04-28 1995-11-07 Nittetsu Hard Kk 耐熱性表面層を形成した連続鋳造モールド
US5787866A (en) 1996-04-12 1998-08-04 Denso Corporation Air-fuel ratio sensor
EP0859233A2 (en) 1997-02-12 1998-08-19 Ngk Insulators, Ltd. Gas sensor
US6274016B1 (en) * 1998-06-29 2001-08-14 Kabushiki Kaisha Riken Nitrogen oxide gas sensor

Non-Patent Citations (2)

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Title
Patent Abstracts of Japan, vol. 012, No. 132 (C-490), Apr. 22, 1988 & JP 62 250151 A (Alps Electric Co. Ltd.), Oct. 31, 1987.
Patent Abstracts of Japan, vol. 1996, No. 03, Mar. 29, 1996 & JP 07 290198 A (Nittetsu Hard KK), Nov. 7, 1995.

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040188321A1 (en) * 2003-03-24 2004-09-30 Sumitomo Electric Industries, Ltd. Wafer holder for semiconductor manufacturing device and semiconductor manufacturing device in which it is installed
US20040247844A1 (en) * 2003-03-28 2004-12-09 Seiko Epson Corporation Ceramic material coating method and ceramic film
US20070176077A1 (en) * 2006-01-30 2007-08-02 Science Applications International Corporation System and method for correction of turbulence effects on laser or other transmission
US7402785B2 (en) * 2006-01-30 2008-07-22 Science Applications International Corporation System and method for correction of turbulence effects on laser or other transmission
EP2763143A4 (en) * 2011-09-27 2016-01-27 Tanaka Precious Metal Ind CONDUCTIVE PARTICLES, METALLIC PASTE, AND ELECTRODE
CN102809634A (zh) * 2012-08-28 2012-12-05 济南大学 一种基于钯杂化四氧化三铁纳米材料构建的气敏传感器
CN106018496A (zh) * 2016-05-20 2016-10-12 太原理工大学 一种高灵敏度低工作温度乙醇气体传感器元件的制备方法

Also Published As

Publication number Publication date
CN1201344C (zh) 2005-05-11
WO2001004915A3 (de) 2002-01-24
EP1145255A2 (de) 2001-10-17
EP1145255B1 (de) 2006-10-18
JP4532047B2 (ja) 2010-08-25
DE50013637D1 (de) 2006-11-30
CN1359526A (zh) 2002-07-17
EP1145255A3 (de) 2002-09-11
WO2001004915A2 (de) 2001-01-18
JP2003504604A (ja) 2003-02-04
DE19932545A1 (de) 2001-01-18

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